Trying to understand center diff. vs. rear vs. front lock

[kcjaz]

I've used all the tools: MTS, Crawl, turn assist, center, front and rear diffs. They all have their place.

One example was two weekends ago, wheeling offroad in snow/ice on a steep off camber downhill. Crawl control worked pretty well for this. Could I have done it without, yup, but since I had it, I figured I'd use it. It helped reduce the pucker factor.

But I think I misread your question. I haven't mixed and matched crawl control and lockers. I usually turn crawl control off unless I explicitly want it. I haven't noticed MTS activating when I was locked (not saying it can't happen, I just haven't seen that).

Also, I don't often lock my front axle, but lock my rear more frequently. In this situation, I'd think there is the possibility to have wheels turning at different speeds and trigger MTS.

Side note: I turn off VSC and RSCA any time I'm offroad.

I can't wait to get my front and rear lockers so I can play with all of the options. One combination is CDL with rear locker only. I think MTS will still do its thing on the from axle. If that's right, I think that's a good argument a front locker doesn't give you much additional capability. Of course, I'd never just add only the rear locker because I want to be able to tell people I'm "triple locked".

 

[kcjaz]

But if three tires are slipping 100% goes to one wheel...

I think, theoretically speaking, if an AWD with an open center diff was stopped with the rear on dry pavement and the front tires were on ice (zero traction), without locking the center diff, it would not be able to move.

A 200’s Torsten center diff would allow the truck to move even w/o the center diff locked. Right?

 

[CharlieS]

I can't wait to get my front and rear lockers so I can play with all of the options. One combination is CDL with rear locker only. I think MTS will still do its thing on the from axle. If that's right, I think that's a good argument a front locker doesn't give you much additional capability. Of course, I'd never just add only the rear locker because I want to be able to tell people I'm "triple locked".

There are absolutely times when front and rear lockers add capability, climbing things with relative ease that it wouldn't otherwise.

 

[Sandroad]

I think, theoretically speaking, if an AWD with an open center diff was stopped with the rear on dry pavement and the front tires were on ice (zero traction), without locking the center diff, it would not be able to move.

A 200’s Torsten center diff would allow the truck to move even w/o the center diff locked. Right?

It really is just a theoretical question. Every all wheel drive and four wheel drive vehicle sold in the U.S. for the past decades have traction control aids that brake a low traction tire(s) so the vehicle can move in your scenario.

 

[CharlieS]

Pretty decent video explaining the features:

 

[kcjaz]

It really is just a theoretical question. Every all wheel drive and four wheel drive vehicle sold in the U.S. for the past decades have traction control aids that brake a low traction tire(s) so the vehicle can move in your scenario.

Agreed. That's why I prefaced my question with "theoretically speaking"... In theory, a Torsen LSD diff would lock when loss of traction is felt on either the front or rear axles resulting in the vehicle in my example being able to move (without electronic traction control using ABS). I think the amount of lock (or limited slip) can vary with the design. I'm over my machine design head here. Lots of interesting stuff on the internet if you google Torsen. Many good videos explaining how it works.

 

[slipkid13]

The 200 is an all-wheel-drive vehicle and AWD is what you have with center diff unlocked (normal, most of the time). Locking the center diff essentially turns your AWD vehicle to a 4WD vehicle. With the center diff locked the output shafts from the transfer case (front and rear) are locked and will spin the same which sends the power 50/50 front and rear. So hitting the center diff lock in an AWD vehicle is the same as shifting to 4hi in a part time 4WD pickup (like my Tacoma). In either case, though the front and rear differentials are still open meaning they allow different rotational, speed left and right. The next step is adding front and rear differential lockers. I this is the only way to get all four wheels to rotate the same regardless of traction.

Generally speaking the 200’s all wheel drive system with traction control and MTS is pretty awesome. It handles most situations. I tend to only use the center diff lock on steep inclines (off-road of course) and I often shut it off going downhill off-road. Especially if there’s hairpin turns or situations where I feel the need I need to maneuver in tight spots.

Here’s an an article that explains the basics.

What does a center locking differential do? | everything about diff locks in simplest way - Off Roading Pal

Center differential lock gives you the ability to lock front and rear axles to divide the engine power (rotational force & rotational speed) equally between both front and rear wheels. This may bit confusing to you. But don’t worry. I’ll explain in simplest form, why these things are important...

www.offroadingpal.com

I thought the 200 was 4WD not AWD. I understand the torsen diff helps vector torque to front/rear but I thought all 4 wheels are driven all the time. My understanding of AWD is that in normal driving the vehicle i only powering 1 or 2 wheels until slip is detected then power is placed to the other wheels to assist in traction.

 

[lx200inAR]

Agreed. That's why I prefaced my question with "theoretically speaking"... In theory, a Torsen LSD diff would lock when loss of traction is felt on either the front or rear axles resulting in the vehicle in my example being able to move (without electronic traction control using ABS). I think the amount of lock (or limited slip) can vary with the design. I'm over my machine design head here. Lots of interesting stuff on the internet if you google Torsen. Many good videos explaining how it works.

Yes with the Torsen, one wheel on each axle would have to slip to get stuck, even unlocked. I’ll caveat that with saying that a Torsen LSD is a torque multiplying design, so if there is 0 force stopping the slipping wheel, then the diff can’t apply torque to the non slipping wheel. This is a key reason I suspect the CDL is usually included on Toyota Torsen based center diffs.

 

[lx200inAR]

I thought the 200 was 4WD not AWD. I understand the torsen diff helps vector torque to front/rear but I thought all 4 wheels are driven all the time. My understanding of AWD is that in normal driving the vehicle i only powering 1 or 2 wheels until slip is detected then power is placed to the other wheels to assist in traction.

I don’t think there is a hard set rule on what AWD and 4WD really mean. FWD with torque splitting on slippage to the rear is a tactic used by some vehicles, but also biased full time AWD is another tactic. I’m pretty sure most Subarus are considered AWD, and I know my WRX was closer to the 200series design than to the FWD setup. I’m pretty sure it had LSD at all 3 diffs.

 

[slipkid13]

I don’t think there is a hard set rule on what AWD and 4WD really mean. FWD with torque splitting on slippage to the rear is a tactic used by some vehicles, but also biased full time AWD is another tactic. I’m pretty sure most Subarus are considered AWD, and I know my WRX was closer to the 200series design than to the FWD setup. I’m pretty sure it had LSD at all 3 diffs.

I always understood AWD as 90% FWD (usually, could be RWD) until some slippage was detected. Then power is placed to other wheels. 4WD always drives all wheels.

Is there a scenario where a 200 is only driving 2 wheels?

Sort of related is there a reason Toyota didn't do a FWD/4HI/4LO setup like the 4Runner on the 200?

 

[lx200inAR]

I always understood AWD as 90% FWD (usually, could be RWD) until some slippage was detected. Then power is placed to other wheels. 4WD always drives all wheels.

Is there a scenario where a 200 is only driving 2 wheels?

Sort of related is there a reason Toyota didn't do a FWD/4HI/4LO setup like the 4Runner on the 200?

Like I said, I believe you’d be hard pressed to nail down a clear cut definition. The 200 system is far superior to the 4Runner. No 4Runner that I know of is FWD (without something broken). There are some 4Runners that have a Full-Time 4wd system, or AWD, however you want to call it. Then standard part time 4WD with 4Hi/4Lo and then RWD.

What you are describing, if I had to put a name to it, would be an active AWD system.

A lot of people make the split at the function of the center diff. If it’s locked, it’s 4WD and if it’s open or LSD it’s AWD. Which makes the 200 float between the 2.

 

[kcjaz]

AWD/FWD, there are many ways to skin the cat and as @lx200inAR says no clear cut definition. Here are a couple good videos. The first one has some points that I had never considered as I often unlock my center diff off road when I don't think I need it. The guy advocates locking it all the time when off road. I hadn't considered things like parking on an incline with center diff locked vs. unlocked. I knew I could push a vehicle with one wheel jacked off the ground (that why you use wheel chocks) but had not ever thought of locking the center diff to prevent that.

 

[bloc]

Sort of related is there a reason Toyota didn't do a FWD/4HI/4LO setup like the 4Runner on the 200?

By driving all four wheels for normal use they’ve reduced the load on individual driveline components and increased durability.

Not needing to engage any special modes makes it pretty idiot-proof which always seems to be a goal of auto manufacturers.

I also believe it has to do with the amount of power our vehicles have, when considering high center of gravity and short wheelbase. I had the front driveshaft out while troubleshooting a driveline noise and in the dry the difference in behavior under WOT was dramatic.. bordering on unsafe. It was darting all over the road. In the wet it was absolutely unsafe. and this is a vehicle that with the stock AWD system functioning most people describe as very planted and sure footed, even in the rain or snow. Sure you could engage 4WD but now you are binding the drivetrain through any tight turns.

 

[AnyMal]

This is the type of thread I needed. And i always say to ask and make new posts. The most fruitful convos can come out of nowhere.

Very interesting hearing how you all run synergy with the on board aid systems.

It make’s sense there are scenarios where you dont want to risk any slow intervention and just lock up.

On that topic, I had also been reading / watching about e locker vs air engagement mechanisms.

Apparently harrop has addressed the engagement slop in their unit.

I’ve always thought I would go E lock harrop eventually, but I have to leave pavement at some point.



Apparently the older design would hesitate to engage whereas the air systems lock up almost instantly without much play required in the lock ring.

Any feedback from the pros here?

 

[AnyMal]

Here is the original video that taught me about the pros and cons of the different diff lockers:

First 3 minutes shows it well.


Maybe the crawl features would work well with this caveat (allegedly solved) with E lockers in the disengagement roll backs.

 

[bloc]

Apparently the older design would hesitate to engage whereas the air systems lock up almost instantly without much play required in the lock ring.

Yeah the old design needed a significant portion of a revolution to get the pins locked in and lock the diff. Usually not much of an issue, but the scenario I read about was one where you'd be locked and moving forward, then need to reverse.. and this would unlock the diff for the beginning of that reverse maneuver.

Seemed like an edge case but it's not hard to imagine being twisted up on a steep trail needing the locker, then needing to reverse to get out of that bad situation, and suddenly you lose a significant part of the control and predictability your locked diff provided.

If they addressed this weakness of the old design that would be a huge win, IMO. I'm not in the market for lockers but in the past the positive locked or not-locked nature was the primary reason I'd consider tolerating the reliability issues of ARBs over the more reliable but at the time quirky harrop.

 

[Tex68w]

I was a huge ARB fan and had planned to go with them for the 200 but with the 16+ rear changes it made it a little more difficult and then combining that with the updated Eaton-Harrop engagement it was a no brainier for me to go electric for the rear.

 

[CharlieS]

I think, theoretically speaking, if an AWD with an open center diff was stopped with the rear on dry pavement and the front tires were on ice (zero traction), without locking the center diff, it would not be able to move.

A 200’s Torsten center diff would allow the truck to move even w/o the center diff locked. Right?

I

This is the type of thread I needed. And i always say to ask and make new posts. The most fruitful convos can come out of nowhere.

Very interesting hearing how you all run synergy with the on board aid systems.

It make’s sense there are scenarios where you dont want to risk any slow intervention and just lock up.

On that topic, I had also been reading / watching about e locker vs air engagement mechanisms.

Apparently harrop has addressed the engagement slop in their unit.

I’ve always thought I would go E lock harrop eventually, but I have to leave pavement at some point.



Apparently the older design would hesitate to engage whereas the air systems lock up almost instantly without much play required in the lock ring.

Any feedback from the pros here?

Good video. I'd heard the criticisms, but never experienced them on trail. Once engaged, they're transparent to the driver. That video helped to explain why that may be. Thanks!

 

[cruiseroutfit]

I was a huge ARB fan and had planned to go with them for the 200 but with the 16+ rear changes it made it a little more difficult and then combining that with the updated Eaton-Harrop engagement it was a no brainier for me to go electric for the rear.

Have you F/R installed Harrop's on your 16+? The rear is a non-issue with ARB, it's the front of the US spec URJ200 w/8 speed (and 3.307) gears that is the issue for ARB, Harrop and Eaton (unless something has changed recently).

(ARB's Application Guide)

Looking at Harrops current application guide, they show the same Front and Rear locker for all 2007-2021 200's. While true for Australia, this is not the case for the US URJ200 which got a re-gear along with the 8 speed in MY2016.

(Harrops Application Guide)

Interestingly Eaton's E-Locker application guide shows the front and rear working for all 2007-2018 (cutoff of their app guide) which is not correct imo. We list the same locker (our part# EAT14217) for "Eaton E-Locker 2008-2015 200/570 FRONT". If someone knows how to make this fit the 16+, I'm all ears.

We've added ARB or Eaton E-Lockers in combination with re-gear to dozen+ MY16+ 200's. The team from Slee and myself worked with ARB to spec a front locker specific to the 3.307 diff BUT most customers adding a locker to the front of their vehicle are also adding larger tires and weight and thus the re-gear option works quite suitably using 07-15 parts. We stock them for that reason.

 

[Tex68w]

Have you F/R installed Harrop's on your 16+? The rear is a non-issue with ARB, it's the front of the US spec URJ200 w/8 speed (and 3.307) gears that is the issue for ARB, Harrop and Eaton (unless something has changed recently).

View attachment 3193471
(ARB's Application Guide)

Looking at Harrops current application guide, they show the same Front and Rear locker for all 2007-2021 200's. While true for Australia, this is not the case for the US URJ200 which got a re-gear along with the 8 speed in MY2016.

View attachment 3193469
(Harrops Application Guide)

Interestingly Eaton's E-Locker application guide shows the front and rear working for all 2007-2018 (cutoff of their app guide) which is not correct imo. We list the same locker (our part# EAT14217) for "Eaton E-Locker 2008-2015 200/570 FRONT". If someone knows how to make this fit the 16+, I'm all ears.

We've added ARB or Eaton E-Lockers in combination with re-gear to dozen+ MY16+ 200's. The team from Slee and myself worked with ARB to spec a front locker specific to the 3.307 diff BUT most customers adding a locker to the front of their vehicle are also adding larger tires and weight and thus the re-gear option works quite suitably using 07-15 parts. We stock them for that reason.

I meant front, typo and/or brain diarrhea lol. Just the Eaton in the rear, doubt I’ll lock the front given what this truck is used for.